In general, the invention provides a genetically modified ungulate that contains either part or all of a xenogenous antibody gene locus, which undergoes rearrangement and expresses a diverse population of antibody molecules. In particular, the xenogenous antibody gene may be of human origin. In addition, the present invention provides for an ungulate in which expression of the endogenous antibody genes is either reduced or eliminated. The genetic modifications in the ungulate (for example, bovine) are made using a combination of nuclear transfer and molecular techniques. These cloned, transgenic ungulate (e.g., bovines) provide a replenishable, theoretically infinite supply of xenogenous polyclonal antibodies, particularly human antibodies, which have use, e.g., as therapeutics, diagnostics and for purification purposes. The invention also features methods for reducing the amount of endogenous antibody in non-human mammals, such as ungulates, that express both endogenous and xenogenous antibody. These methods increase the percentage of xenogenous B-cells and xenogenous antibody expressed by the mammals.
In 1890, Shibasaburo Kitazato and Emil Behring reported an experiment with extraordinary results; particularly, they demonstrated that immunity can be transferred from one animal to another by taking serum from an immune animal and injecting it into a non-immune one. This landmark experiment laid the foundation for the introduction of passive immunization into clinical practice. Today, the preparation and use of human immunoglobulin (Ig) for passive immunization is standard medical practice. In the United States alone, there is a $1,400,000,000 per annum market for human Ig, and each year more than 16 metric tons of human antibody is used for intravenous antibody therapy. Comparable levels of consumption exist in the economies of most highly industrialized countries, and the demand can be expected to grow rapidly in developing countries. Currently, human antibody for passive immunization is obtained from the pooled serum of human donors. This means that there is an inherent limitation in the amount of human antibody available for therapeutic and prophylactic usage. Already, the demand exceeds the supply and severe shortfalls in availability have been routine. Thus improved methods are needed to generate human antibody that is free of non-human antibody for clinical applications.
For example, improved methods and enhanced transgenic animals that produce polyclonal antibodies of a desired species (e.g., human Igs) in the bloodstream and which produce an array of different antibodies which are specific to a desired antigen would be highly desirable. Most especially, the production of human Igs in ungulates, such as cows, would be particularly beneficial given that (1) cows could produce large quantities of antibody, (2) cows could be immunized with human or other pathogens and (3) cows could be used to make human antibodies against human antigens. The availability of large quantities of polyclonal antibodies would be advantageous for treatment and prophylaxis for infectious disease, modulation of the immune system, removal of undesired human cells such as cancer cells, and modulation of specific human molecules.